1. Field of the Invention
The present invention relates to an optical part driving device, for example, an optical part driving device which is useful for an optical interferometer used in an optical measurement technical field, and an optical interferometer to which the optical part driving device is applied.
2. Description of the Related Art
In optical interferometers which the Michelson interferometer represents, an incident light is divided into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by using a beam splitter. Two lights reflected on each mirror disposed so as to be perpendicular to each optical path are multiplexed by a beam splitter again.
At the same time, a stage on which one mirror is mounted is moved at a constant speed and straightly. The optical path difference between the two lights reflected on the two mirrors is caused. A variety of intensity of interference fringes can be observed. The variety of intensity of interference fringes is fetched by the photo-detector as an electric signal.
The wavelength of a light can be measured more precisely by moving the movable mirror straight and a long distance.
As a driving device for a movable mirror, a ball screw mechanism, a timing belt device, a wire device or the like has been known.
In case of a timing belt device, a tension is applied to a timing belt by one tension pulley provided on one side of the timing belt.
However, when a timing belt device is used as a driving device for a movable mirror, in case of a low percentage of an engagement of a timing belt with a driving timing pulley, there is some possibility that the engagement fails during the drive of a timing belt device.
Because only one tension pulley is provided on one side of a timing belt, there is a problem about an initial moving time, in particular, a problem in which when the movable mirror is moved in right and left directions by using one tension pulley, a time difference is slightly caused between a right direction and a left one.
In order to solve the above-described problems, an object of the present invention is to provide an optical part driving device in which the percentage of the engagement of a timing belt with a driving timing pulley is increased in order to prevent the above failure in the engagement, and in which an optical part is moved at the same initial speed in both right and left directions in order to improve the accuracy thereof.
Another object of the present invention is to provide an optical interferometer in which the above optical part driving device is provided.
That is, in accordance with one aspect of the present invention, the optical part driving device for moving an optical part, comprises;
a driving timing pulley,
a pair of driven timing pulleys,
a timing belt wound by the driving timing pulley and the driven timing pulleys and connected with the optical part between the pair of driven timing pulleys, and
a pair of tension pulleys for tensing the timing belt on both sides of the driving timing pulley.
As an optical part, a movable mirror for an optical interferometer, which moves straightly, is used. However, the present invention is not limited to this. Any other optical part may be used.
The tension pulley may be a timing pulley which has teeth corresponding to the timing belt or may be a simple pulley which has no teeth.
According to the present invention, because the optical part is connected with the timing belt wound by the driving timing pulley and a pair of driven timing pulleys between the pair of driven timing pulleys and a pair of tension pulleys for tensing the timing belt is provided on both sides of the driving timing pulley, the percentage of an engagement of the timing belt with the driving timing pulley is increased by a pair of tension pulleys provided for the timing belt on both sides of the driving timing pulley. As a result, the problem about the failure in the engagement can be solved. Further, the optical part can be moved at the same initial speed in both directions.
The driving timing pulley may be disposed at an approximate center between the pair of driven timing pulleys.
According to the present invention, because the driving timing pulley is disposed at an approximate center between the pair of driven timing pulleys, the distance between the driving timing pulley and one driven timing pulley is the same as one between the driving timing pulley and the other driven timing pulley. As a result, the optical part can be moved at the same initial speed in both directions.
In accordance with another aspect of the present invention, the optical interferometer is one wherein
the plurality of optical parts are separated into a fixed optical part which is fixed to a casing and a movable optical part which is movable with respect to the casing, and
the optical interferometer comprises an optical part driving device for moving the movable optical part comprising;
a driving timing pulley,
a pair of driven timing pulleys,
a timing belt wound by the driving timing pulley and the driven timing pulleys and connected with the movable optical part between the pair of driven timing pulleys, and
a pair of tension pulleys for tensing the timing belt on both sides of the driving timing pulley.
For example, as an optical part, a beam splitter or a reflector is used.
According to the present invention, because the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable optical part a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently small.
Because the optical interferometer comprises the above optical part driving device, the optical part can be moved at the same initial speed in both directions. The wavelength of a light can be measured more precisely.
In accordance with another aspect of the present invention, the optical interferometer in which a reference light and a light to be measured branch into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by a beam splitter, and in which after the reflected light and the transmitted light are reflected on a plurality of reflecting members each other in each optical path, the reflected light and the transmitted light are multiplexed by the beam splitter to receive the multiplexed light by a photo-detector, is one wherein
the plurality of reflecting members are separated into a fixed reflecting member which is fixed to a casing and a movable reflecting member which is movable with respect to the casing, and
the optical interferometer comprises an optical part driving device for moving the movable reflecting member comprising;
a driving timing pulley,
a pair of driven timing pulleys,
a timing belt wound by the driving timing pulley and the driven timing pulleys and connected with the movable reflecting member between the pair of driven timing pulleys, and
a pair of tension pulleys for tensing the timing belt on both sides of the driving timing pulley.
For example, a representative reflecting member is a mirror. Instead of a mirror, for example, a corner cube or a reflector may be used.
The photo-detector is one for fetching a variety of intensity of interference fringes as an electric signal.
According to the present invention, because the movable reflecting member is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable reflecting member a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently small.
Because the optical interferometer comprises the above optical part driving device, the movable reflecting member can be moved at the same initial speed in both directions. The wavelength of a light can be measured more precisely.
A pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other may be provided, and a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member may be disposed between the pair of fixed reflecting members.
According to the present invention, because a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member is disposed between the pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other, a wide range in which an optical path difference between two lights is caused can be obtained by moving the pair of movable reflecting members between the pair of fixed reflecting members on an optical axis which is approximately parallel to the optical axis of the reference light so as to reflect each light totally.